The present application relates to photovoltaic devices, and more particularly to a thin film photovoltaic device using a cracked absorber layer.
Photovoltaic cells are devices that generate electric power from electromagnetic energy (e.g., sunlight) incident thereon. Thin film photovoltaic devices employing thin layers of semiconductor material with a thickness in a range from a few nanometers to tens of micrometers have been developed to minimize the amount of semiconductor material used to fabricate the photovoltaic devices. Since very small quantities of semiconductor materials are used, costs of thin film photovoltaic devices can be lower than those for silicon-based bulk devices.
Thin film photovoltaic devices contain an active layer (i.e., absorber layer) which is of a light absorbing material that generates charge carriers upon exposure to light. One challenge faced in fabrication of thin film photovoltaic devices is the ability to produce a defect-free absorber layer. The absorber layer is typically formed by a spalling process in which a thin layer of a semiconductor material that provides the absorber layer is exfoliated or peeled from a thicker base substrate. However, due to the mechanical frangibility of the thin film, it is very difficult to produce a crack-free absorber layer at a thickness range of interest (typically less than 50 μm). Photovoltaic devices utilizing the crack-containing absorber layers can suffer from poor performance because the cracks can contain material from later formed conductive layers, causing electrical shorts across the cracks.
Cracks in absorber layers are detrimental to the performance of photovoltaic devices. Absorber layers containing cracks are normally discarded, contributing to decreased yield and higher costs. Therefore, a method that allows utilizing a crack-containing thin film as the absorber layer in photovoltaic devices remains needed.